An indoor unit of an air conditioner known in the art is provided with an air deflector component for guiding upper and lower air outflow directions of the air conditioner. With such an existing air deflector, a driving motor is fixedly mounted to a base, and when the air deflector is rotating, the position of the rotational axis is stationary. In order to make room for the rotation of the deflector, usually a rotation space is provided around the air deflector and the air outlet, and gaps are formed between the air outlet and the air deflector while the air deflector is in a fully closed arrangement when the air conditioner is not in operation (gaps are formed at the left, right, upper and lower sides). This impairs the appearance aesthetics of the air conditioner. Moreover, the movement of the air deflector is simple, merely involving rotational movement about a stationary axis, and a variety of air supply angles cannot be obtained. Meanwhile, as the air outlet is not completely closed, dust, mildew and the like can be introduced into the interior of the indoor unit of the air conditioner and thus impair the cleanliness of indoor air.